Age- and diet-dependent requirement of DJ-1 for glucose homeostasis in mice with implications for human type 2 diabetes

A reduced proteomic signature in critically ill Covid-19 patients determined with plasma antibody micro-array and machine learning

BACKGROUND

COVID-19 is a complex, multi-system disease with varying severity and symptoms. Identifying changes in critically ill COVID-19 patients' proteomes enables a better understanding of markers associated with susceptibility, symptoms, and treatment. We performed plasma antibody microarray and machine learning analyses to identify novel proteins of COVID-19.

METHODS

A case-control study comparing the concentration of 2000 plasma proteins in age- and sex-matched COVID-19 inpatients, non-COVID-19 sepsis controls, and healthy control subjects. Machine learning was used to identify a unique proteome signature in COVID-19 patients. Protein expression was correlated with clinically relevant variables and analyzed for temporal changes over hospitalization days 1, 3, 7, and 10. Expert-curated protein expression information was analyzed with Natural language processing (NLP) to determine organ- and cell-specific expression.

RESULTS

Machine learning identified a 28-protein model that accurately differentiated COVID-19 patients from ICU non-COVID-19 patients (accuracy = 0.89, AUC = 1.00, F1 = 0.89) and healthy controls (accuracy = 0.89, AUC = 1.00, F1 = 0.88). An optimal nine-protein model (PF4V1, NUCB1, CrkL, SerpinD1, Fen1, GATA-4, ProSAAS, PARK7, and NET1) maintained high classification ability. Specific proteins correlated with hemoglobin, coagulation factors, hypertension, and high-flow nasal cannula intervention (P < 0.01). Time-course analysis of the 28 leading proteins demonstrated no significant temporal changes within the COVID-19 cohort. NLP analysis identified multi-system expression of the key proteins, with the digestive and nervous systems being the leading systems.

CONCLUSIONS

The plasma proteome of critically ill COVID-19 patients was distinguishable from that of non-COVID-19 sepsis controls and healthy control subjects. The leading 28 proteins and their subset of 9 proteins yielded accurate classification models and are expressed in multiple organ systems. The identified COVID-19 proteomic signature helps elucidate COVID-19 pathophysiology and may guide future COVID-19 treatment development.

Diabetes: a tipping point in neurodegenerative diseases

Diabetes is associated with an increased risk and progression of Alzheimer's (AD) and Parkinson's (PD) diseases. Conversely, diabetes may confer neuroprotection against amyotrophic lateral sclerosis (ALS). It has been posited that perturbations in glucose and insulin regulation, cholesterol metabolism, and mitochondrial bioenergetics defects may underlie the molecular underpinnings of diabetes effects on the brain. Nevertheless, the precise molecular mechanisms remain elusive. Here, we discuss the evidence from molecular, epidemiological, and clinical studies investigating the impact of diabetes on neurodegeneration and highlight shared dysregulated pathways between these complex comorbidities. We also discuss promising antidiabetic drugs, molecular diagnostics currently in clinical trials, and outstanding questions and challenges for future pursuit.

PARK7 Catalyzes Stereospecific Detoxification of Methylglyoxal Consistent with Glyoxalase and Not Deglycase Function

The protein PARK7 (also known as DJ-1) has been implicated in several diseases, with the most notable being Parkinson's disease. While several molecular and cellular roles have been ascribed to DJ-1, there is no real consensus on what its true cellular functions are and how the loss of DJ-1 function may contribute to the pathogenesis of Parkinson's disease. Recent reports have implicated DJ-1 in the detoxification of several reactive metabolites that are produced during glycolytic metabolism, with the most notable being the α-oxoaldehyde species methylglyoxal. While it is generally agreed that DJ-1 is able to metabolize methylglyoxal to lactate, the mechanism by which it does so is hotly debated with potential implications for cellular function. In this work, we provide definitive evidence that recombinant DJ-1 produced in human cells prevents the stable glycation of other proteins through the conversion of methylglyoxal or a related alkynyl dicarbonyl probe to their corresponding α-hydroxy carboxylic acid products. This protective action of DJ-1 does not require a physical interaction with a target protein, providing direct evidence for a glutathione-free glyoxalase and not a deglycase mechanism of methylglyoxal detoxification. Stereospecific liquid chromatography-mass spectrometry (LC-MS) measurements further uncovered the existence of nonenzymatic production of racemic lactate from MGO under physiological buffer conditions, whereas incubation with DJ-1 predominantly produces l-lactate. Collectively, these studies provide direct support for the stereospecific conversion of MGO to l-lactate by DJ-1 in solution with negligible or no contribution of direct protein deglycation.

Skeletal muscle-specific DJ-1 ablation-induced atrogenes expression and mitochondrial dysfunction contributing to muscular atrophy

BACKGROUND

DJ-1 is a causative gene for Parkinson's disease. DJ-1-deficient mice develop gait-associated progressive behavioural abnormalities and hypoactive forearm grip strength. However, underlying activity mechanisms are not fully explored.

METHODS

Western blotting and quantitative real-time polymerase chain reaction approaches were adopted to analyse DJ-1 expression in skeletal muscle from aged humans or mice and compared with young subjects. Skeletal muscle-specific-DJ-1 knockout (MDKO) mice were generated, followed by an assessment of the physical activity phenotypes (grip strength, maximal load capacity, and hanging, rotarod, and exercise capacity tests) of the MDKO and control mice on the chow diet. Muscular atrophy phenotypes (cross-sectional area and fibre types) were determined by imaging and quantitative real-time polymerase chain reaction. Mitochondrial function and skeletal muscle morphology were evaluated by oxygen consumption rate and electron microscopy, respectively. Tail suspension was applied to address disuse atrophy. RNA-seq analysis was performed to indicate molecular changes in muscles with DJ-1 ablation. Dual-luciferase reporter assays were employed to identify the promoter region of Trim63 and Fbxo32 genes, which were indirectly regulated by DJ-1 via the FoxO1 pathway. Cytoplasmic and nuclear fractions of DJ-1-deleted muscle cells were analysed by western blotting. Compound 23 was administered into the gastrocnemius muscle to mimic the of DJ-1 deletion effects.

RESULTS

DJ-1 expression decreased in atrophied muscles of aged human (young men, n = 2; old with aged men, n = 2; young women, n = 2; old with aged women, n = 2) and immobilization mice (n = 6, P < 0.01). MDKO mice exhibited no body weight difference compared with control mice on the chow diet (Flox, n = 8; MDKO, n = 9). DJ-1-deficient muscles were slightly dystrophic (Flox, n = 7; MDKO, n = 8; P < 0.05), with impaired physical activities and oxidative capacity (n = 8, P < 0.01). In disuse-atrophic conditions, MDKO mice showed smaller cross-sectional area (n = 5, P < 0.01) and more central nuclei than control mice (Flox, n = 7; MDKO, n = 6; P < 0.05), without alteration in muscle fibre types (Flox, n = 6; MDKO, n = 7). Biochemical analysis indicated that reduced mitochondrial function and upregulated of atrogenes induced these changes. Furthermore, RNA-seq analysis revealed enhanced activity of the FoxO1 signalling pathway in DJ-1-ablated muscles, which was responsible for the induction of atrogenes. Finally, compound 23 (an inhibitor of DJ-1) could mimic the effects of DJ-1 ablation in vivo.

CONCLUSIONS

Our results illuminate the crucial of skeletal muscle DJ-1 in the regulation of catabolic signals from mechanical stimulation, providing a therapeutic target for muscle wasting diseases.

Aging, Parkinson's Disease, and Models: What Are the Challenges?

Parkinson's disease (PD) is a chronic, neurodegenerative condition characterized by motor symptoms such as bradykinesia, rigidity, and tremor, alongside multiple nonmotor symptoms. The appearance of motor symptoms is linked to progressive dopaminergic neuron loss within the substantia nigra. PD incidence increases sharply with age, suggesting a strong association between mechanisms driving biological aging and the development and progression of PD. However, the role of aging in the pathogenesis of PD remains understudied. Numerous models of PD, including cell models, toxin-induced models, and genetic models in rodents and nonhuman primates (NHPs), reproduce different aspects of PD, but preclinical studies of PD rarely incorporate age as a factor. Studies using patient neurons derived from stem cells via reprogramming methods retain some aging features, but their characterization, particularly of aging markers and reproducibility of neuron type, is suboptimal. Investigation of age-related changes in PD using animal models indicates an association, but this is likely in conjunction with other disease drivers. The biggest barrier to drawing firm conclusions is that each model lacks full characterization and appropriate time-course assessments. There is a need to systematically investigate whether aging increases the susceptibility of mouse, rat, and NHP models to develop PD and understand the role of cell models. We propose that a significant investment in time and resources, together with the coordination and sharing of resources, knowledge, and data, is required to accelerate progress in understanding the role of biological aging in PD development and improve the reliability of models to test interventions.

Persulfidation of DJ-1: Mechanism and Consequences

DJ-1 (also called PARK7) is a ubiquitously expressed protein involved in the etiology of Parkinson disease and cancers. At least one of its three cysteine residues is functionally essential, and its oxidation state determines the specific function of the enzyme. DJ-1 was recently reported to be persulfidated in mammalian cell lines, but the implications of this post-translational modification have not yet been analyzed. Here, we report that recombinant DJ-1 is reversibly persulfidated at cysteine 106 by reaction with various sulfane donors and subsequently inhibited. Strikingly, this reaction is orders of magnitude faster than C106 oxidation by H₂O₂, and persulfidated DJ-1 behaves differently than sulfinylated DJ-1. Both these PTMs most likely play a dedicated role in DJ-1 signaling or protective pathways.

Proteomics profiles of blood glucose-related proteins involved in a Chinese longevity cohort

BACKGROUND

High blood glucose level is one of the main characteristics of diabetes mellitus. Based on previous studies, it is speculated longevity families may have certain advantages in blood glucose regulation. However, limited information on these items has been reported. The purpose of this study was to profile differences of plasma proteomics between longevity subjects (with normal fructosamine (FUN) level) and non-longevity area participants (with exceeding standard FUN level).

METHODS

In this study, a TMT-based proteomics analysis was used to profile differences of plasma proteomics between longevity subjects (with normal FUN level) and non-longevity area participants (with exceeding standard FUN level). Results were validated by Luminex detection.

RESULTS

A total of 155 differentially expressed proteins (DEPs) were identified between these two groups. The DEPs related to blood glucose regulation were mainly involved in glycolysis/gluconeogenesis, pyruvate metabolism and propanoate metabolism, and most of the DEPs were contained in carbohydrate metabolism, PI3K-Akt pathway, glucagon signaling pathway and inflammatory response. Validation by Luminex detection confirmed that CD163 was down-regulated, and SPARC, PARK 7 and IGFBP-1 were up-regulated in longevity participants.

CONCLUSIONS

This study not only highlighted carbohydrate metabolism, PI3K-Akt pathway, glucagon signaling pathway and inflammatory response may play important roles in blood glucose regulation, but also indicated that YWHAZ, YWHAB, YWHAG, YWHAE, CALM3, CRP, SAA2, PARK 7, IGFBP1 and VNN1 may serve as potential biomarkers for predicting abnormal blood glucose levels.

Type 2 diabetes mellitus augments Parkinson's disease risk or the other way around: Facts, challenges and future possibilities

About 10% of the adult population is living with type 2 diabetes mellitus (T2DM) and 1% of the population over 60 years of age is suffering from Parkinson's disease (PD). A school of thought firmly believes that T2DM, an age-related disease, augments PD risk. Such relationship is reflected from the severity of PD symptoms in drug naive subjects possessing T2DM. Onset of Parkinsonian feature in case controls possessing T2DM corroborates the role of hyperglycemia in PD. A few cohort, meta-analysis and animal studies have shown an increased PD risk owing to insulin resistance. High fat diet and role of insulin signaling in the regulation of sugar metabolism, oxidative stress, α-synuclein aggregation and accumulation, inflammatory response and mitochondrial function in PD models and sporadic PD further connect the two. Although little is reported about the implication of PD in hyperglycemia and T2DM, a few studies have also contradicted. Ameliorative effect of anti-diabetic drugs on Parkinsonian symptoms and vague outcome of anti-PD medications in T2DM patients also suggest a link. The article reviews the literature supporting augmented risk of one by the other, analysis of proof of the concept, facts, challenges, future possibilities and standpoint on the subject.

Metabolomics as a Crucial Tool to Develop New Therapeutic Strategies for Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer's (AD), Parkinson's (PD), and amyotrophic lateral sclerosis (ALS), share common pathological mechanisms, including metabolism alterations. However, their specific neuronal cell types affected and molecular biomarkers suggest that there are both common and specific alterations regarding metabolite levels. In this review, we were interested in identifying metabolite alterations that have been reported in preclinical models of NDs and that have also been documented as altered in NDs patients. Such alterations could represent interesting targets for the development of targeted therapy. Importantly, the translation of such findings from preclinical to clinical studies is primordial for the study of possible therapeutic agents. We found that N-acetyl-aspartate (NAA), myo-inositol, and glutamate are commonly altered in the three NDs investigated here. We also found other metabolites commonly altered in both AD and PD. In this review, we discuss the studies reporting such alterations and the possible pathological mechanism underlying them. Finally, we discuss clinical trials that have attempted to develop treatments targeting such alterations. We conclude that the treatment combination of both common and differential alterations would increase the chances of patients having access to efficient treatments for each ND.

PARK7 deficiency inhibits fatty acid β-oxidation via PTEN to delay liver regeneration after hepatectomy

Background & aims

Transient regeneration–associated steatosis (TRAS) is a process of temporary hepatic lipid accumulation and is essential for liver regeneration by providing energy generated from fatty acid β‐oxidation, but the regulatory mechanism underlying TRAS remains unknown. Parkinsonism‐associated deglycase (Park7)/Dj1 is an important regulator involved in various liver diseases. In nonalcoholic fatty liver diseased mice, induced by a high‐fat diet, Park7 deficiency improves hepatic steatosis, but its role in liver regeneration remains unknown

Methods

Park7 knockout (Park7^−/−), hepatocyte‐specific Park7 knockout (Park7^△hep) and hepatocyte‐specific Park7‐Pten double knockout mice were subjected to 2/3 partial hepatectomy (PHx)

Results

Increased PARK7 expression was observed in the regenerating liver of mice at 36 and 48 h after PHx. Park7^−/− and Park7^△hep mice showed delayed liver regeneration and enhanced TRAS after PHx. PPARa, a key regulator of β‐oxidation, and carnitine palmitoyltransferase 1a (CPT1a), a rate‐limiting enzyme of β‐oxidation, had substantially decreased expression in the regenerating liver of Park7^△hep mice. Increased phosphatase and tensin homolog (PTEN) expression was observed in the liver of Park7^△hep mice, which might contribute to delayed liver regeneration in these mice because genomic depletion or pharmacological inhibition of PTEN restored the delayed liver regeneration by reversing the downregulation of PPARa and CPT1a and in turn accelerating the utilization of TRAS in the regenerating liver of Park7^△hep mice

Conclusion

Park7/Dj1 is a novel regulator of PTEN‐dependent fatty acid β‐oxidation, and increasing Park7 expression might be a promising strategy to promote liver regeneration.

Exploring the link between Parkinson's disease and type 2 diabetes mellitus in Drosophila

Parkinson's disease (PD) is the second most common neurodegenerative disease. Diabetes mellitus (DM) is a metabolic disease characterized by high levels of glucose in blood. Recent epidemiological studies have highlighted the link between both diseases; it is even considered that DM might be a risk factor for PD. To further investigate the likely relation of these diseases, we have used a Drosophila PD model based on inactivation of the DJ-1β gene (ortholog of human DJ-1), and diet-induced Drosophila and mouse type 2 DM (T2DM) models, together with human neuron-like cells. T2DM models were obtained by feeding flies with a high sugar-containing medium, and mice with a high fat diet. Our results showed that both fly models exhibit common phenotypes such as alterations in carbohydrate homeostasis, mitochondrial dysfunction or motor defects, among others. In addition, we demonstrated that T2DM might be a risk factor of developing PD since our diet-induced fly and mouse T2DM models present DA neuron dysfunction, a hallmark of PD. We also confirmed that neurodegeneration is caused by increased glucose levels, which has detrimental effects in human neuron-like cells by triggering apoptosis and leading to cell death. Besides, the observed phenotypes were exacerbated in DJ-1β mutants cultured in the high sugar medium, indicating that DJ-1 might have a role in carbohydrate homeostasis. Finally, we have confirmed that metformin, an antidiabetic drug, is a potential candidate for PD treatment and that it could prevent PD onset in T2DM model flies. This result supports antidiabetic compounds as promising PD therapeutics.

Dictyostelium discoideum as a Model for Investigating Neurodegenerative Diseases

The social amoeba Dictyostelium discoideum is a model organism that is used to investigate many cellular processes including chemotaxis, cell motility, cell differentiation, and human disease pathogenesis. While many single-cellular model systems lack homologs of human disease genes, Dictyostelium's genome encodes for many genes that are implicated in human diseases including neurodegenerative diseases. Due to its short doubling time along with the powerful genetic tools that enable rapid genetic screening, and the ease of creating knockout cell lines, Dictyostelium is an attractive model organism for both interrogating the normal function of genes implicated in neurodegeneration and for determining pathogenic mechanisms that cause disease. Here we review the literature involving the use of Dictyostelium to interrogate genes implicated in neurodegeneration and highlight key questions that can be addressed using Dictyostelium as a model organism.

Extracellular Vesicles as Novel Diagnostic and Prognostic Biomarkers for Parkinson's Disease

The elderly population will significantly increase in the next decade and, with it, the proportion of people affected by age-related diseases. Among them, one of the most invalidating is Parkinson's disease (PD), characterized by motor- and non-motor dysfunctions which strongly impair the quality of life of affected individuals. PD is characterized by the progressive degeneration of dopaminergic neurons, with consequent dopamine depletion, and the accumulation of misfolded α-synuclein aggregates. Although 150 years have passed since PD first description, no effective therapies are currently available, but only palliative treatments. Importantly, PD is often diagnosed when the neuronal loss is elevated, making difficult any therapeutic intervention. In this context, two key challenges remain unanswered: (i) the early diagnosis to avoid the insurgence of irreversible symptoms; and (ii) the reliable monitoring of therapy efficacy. Research strives to identify novel biomarkers for PD diagnosis, prognosis, and therapeutic follow-up. One of the most promising sources of biomarkers is represented by extracellular vesicles (EVs), a heterogeneous population of nanoparticles, released by all cells in the microenvironment. Brain-derived EVs are able to cross the blood-brain barrier, protecting their payload from enzymatic degradation, and are easily recovered from biofluids. Interestingly, EV content is strongly influenced by the specific pathophysiological status of the donor cell. In this manuscript, the role of EVs as source of novel PD biomarkers is discussed, providing all recent findings concerning relevant proteins and miRNAs carried by PD patient-derived EVs, from several biological specimens. Moreover, the contribution of mitochondria-derived EVs will be dissected. Finally, the promising possibility to use EVs as source of markers to monitor PD therapy efficacy will be also examined. In the future, larger cohort studies will help to validate these EV-associated candidates, that might be effectively used as non-invasive and robust source of biomarkers for PD.

The Glyoxalase System in Age-Related Diseases: Nutritional Intervention as Anti-Ageing Strategy

The glyoxalase system is critical for the detoxification of advanced glycation end-products (AGEs). AGEs are toxic compounds resulting from the non-enzymatic modification of biomolecules by sugars or their metabolites through a process called glycation. AGEs have adverse effects on many tissues, playing a pathogenic role in the progression of molecular and cellular aging. Due to the age-related decline in different anti-AGE mechanisms, including detoxifying mechanisms and proteolytic capacities, glycated biomolecules are accumulated during normal aging in our body in a tissue-dependent manner. Viewed in this way, anti-AGE detoxifying systems are proposed as therapeutic targets to fight pathological dysfunction associated with AGE accumulation and cytotoxicity. Here, we summarize the current state of knowledge related to the protective mechanisms against glycative stress, with a special emphasis on the glyoxalase system as the primary mechanism for detoxifying the reactive intermediates of glycation. This review focuses on glyoxalase 1 (GLO1), the first enzyme of the glyoxalase system, and the rate-limiting enzyme of this catalytic process. Although GLO1 is ubiquitously expressed, protein levels and activities are regulated in a tissue-dependent manner. We provide a comparative analysis of GLO1 protein in different tissues. Our findings indicate a role for the glyoxalase system in homeostasis in the eye retina, a highly oxygenated tissue with rapid protein turnover. We also describe modulation of the glyoxalase system as a therapeutic target to delay the development of age-related diseases and summarize the literature that describes the current knowledge about nutritional compounds with properties to modulate the glyoxalase system.

Bis-isatin derivatives: design, synthesis, and biological activity evaluation as potent dimeric DJ-1 inhibitors

The PARK7 gene (encode DJ-1 protein) was first discovered as an oncogene and later found to be a causative gene for autosomal recessive early onset Parkinson's disease. DJ-1 has been proposed as a potential therapeutic anticancer target due to its pivotal role in tumorigenesis and cancer progression. Based on the homodimer structure of DJ-1, a series of bis-isatin derivatives with different length linkers were designed, synthesized, and evaluated as dimeric inhibitors targeting DJ-1 homodimer. Among them, DM10 with alkylene chain of C10 displayed the most potent inhibitory activity against DJ-1 deglycase. We further demonstrated that DM10 bound covalently to the homodimer of DJ-1. In human cancer cell lines H1299, MDA-MB-231, BEL7402, and 786-O, DM10 (2.5-20 μM) inhibited the cell growth in a concentration-dependent manner showing better anticancer effects compared with the positive control drug STK793590. In nude mice bearing H1299 cell xenograft, intratumor injection of DM10 (15 mg/kg) produced significantly potent tumor growth inhibition when compared with that caused by STK793590 (30 mg/kg). Moreover, we found that DM10 could significantly enhance N-(4-hydroxyphenyl)retinamide-based apoptosis and erastin-based ferroptosis in H1299 cells. In conclusion, DM10 is identified as a potent inhibitor targeting DJ-1 homodimer with the potential as sensitizing agent for other anticancer drugs, which might provide synergistical therapeutic option for cancer treatment.

Genetic Defects and Pro-inflammatory Cytokines in Parkinson's Disease

Parkinson's disease (PD) is a movement disorder attributed to the loss of dopaminergic (DA) neurons mainly in the substantia nigra pars compacta. Motor symptoms include resting tremor, rigidity, and bradykinesias, while non-motor symptoms include autonomic dysfunction, anxiety, and sleeping problems. Genetic mutations in a number of genes (e.g., LRRK2, GBA, SNCA, PARK2, PARK6, and PARK7) and the resultant abnormal activation of microglial cells are assumed to be the main reasons for the loss of DA neurons in PD with genetic causes. Additionally, immune cell infiltration and their participation in major histocompatibility complex I (MHCI) and/or MHCII-mediated processing and presentation of cytosolic or mitochondrial antigens activate the microglial cells and cause the massive generation of pro-inflammatory cytokines and chemokines, which are all critical for the propagation of brain inflammation and the neurodegeneration in PD with genetic and idiopathic causes. Despite knowing the involvement of several of such immune devices that trigger neuroinflammation and neurodegeneration in PD, the exact disease mechanism or the innovative biomarker that could detect disease severity in PD linked to LRRK2, GBA, SNCA, PARK2, PARK6, and PARK7 defects is largely unknown. The current review has explored data from genetics, immunology, and in vivo and ex vivo functional studies that demonstrate that certain genetic defects might contribute to microglial cell activation and massive generation of a number of pro-inflammatory cytokines and chemokines, which ultimately drive the brain inflammation and lead to neurodegeneration in PD. Understanding the detailed involvement of a variety of immune mediators, their source, and the target could provide a better understanding of the disease process. This information might be helpful in clinical diagnosis, monitoring of disease progression, and early identification of affected individuals.

The Role of DJ-1 in Cellular Metabolism and Pathophysiological Implications for Parkinson's Disease

DJ-1 is a multifunctional protein associated with pathomechanisms implicated in different chronic diseases including neurodegeneration, cancer and diabetes. Several of the physiological functions of DJ-1 are not yet fully understood; however, in the last years, there has been increasing evidence for a potential role of DJ-1 in the regulation of cellular metabolism. Here, we summarize the current knowledge on specific functions of DJ-1 relevant to cellular metabolism and their role in modulating metabolic pathways. Further, we illustrate pathophysiological implications of the metabolic effects of DJ-1 in the context of neurodegeneration in Parkinson´s disease.

DJ-1: A promising therapeutic candidate for ischemia-reperfusion injury

DJ-1 is a multifaceted protein with pleiotropic functions that has been implicated in multiple diseases, ranging from neurodegeneration to cancer and ischemia-reperfusion injury. Ischemia is a complex pathological state arising when tissues and organs do not receive adequate levels of oxygen and nutrients. When the blood flow is restored, significant damage occurs over and above that of ischemia alone and is termed ischemia-reperfusion injury. Despite great efforts in the scientific community to ameliorate this pathology, its complex nature has rendered it challenging to obtain satisfactory treatments that translate to the clinic. In this review, we will describe the recent findings on the participation of the protein DJ-1 in the pathophysiology of ischemia-reperfusion injury, firstly introducing the features and functions of DJ-1 and, successively highlighting the therapeutic potential of the protein.

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DJ-1 has been shown to confer protection in ischemia-reperfusion injury models.

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DJ-1 protection relies on the activation of antioxidant signaling pathways.

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DJ-1 regulates mitochondrial homeostasis during ischemia and reperfusion.

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DJ-1 seems to modulate ion homeostasis during ischemia and reperfusion.

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DJ-1 may represent a promising therapeutic target for ischemia-reperfusion injury.

Dietary betaine prevents obesity through gut microbiota-drived microRNA-378a family

Betaine is a natural compound present in commonly consumed foods and may have a potential role in the regulation of glucose and lipids metabolism. However, the underlying molecular mechanism of its action remains largely unknown. Here, we show that supplementation with betaine contributes to improved high-fat diet (HFD)-induced gut microbiota dysbiosis and increases anti-obesity strains such as Akkermansia muciniphila, Lactobacillus, and Bifidobacterium. In mice lacking gut microbiota, the functional role of betaine in preventing HFD-induced obesity, metabolic syndrome, and inactivation of brown adipose tissues are significantly reduced. Akkermansia muciniphila is an important regulator of betaine in improving microbiome ecology and increasing strains that produce short-chain fatty acids (SCFAs). Increasing two main members of SCFAs including acetate and butyrate can significantly regulate the levels of DNA methylation at host miR-378a promoter, thus preventing the development of obesity and glucose intolerance. However, these beneficial effects are partially abolished by Yin yang (YY1), a common target gene of the miR-378a family. Taken together, our findings demonstrate that betaine can improve obesity and associated MS via the gut microbiota-derived miR-378a/YY1 regulatory axis, and reveal a novel mechanism by which gut microbiota improve host health.

Identification of Disease-Associated Variants by Targeted Gene Panel Resequencing in Parkinson's Disease

Background: Recent advanced technologies, such as high-throughput sequencing, have enabled the identification of a broad spectrum of variants. Using targeted-gene-panel resequencing for Parkinson's disease (PD)-associated genes, we have occasionally found several single-nucleotide variants (SNVs), which are thought to be disease-associated, in PD patients. To confirm the significance of these potentially disease-associated variants, we performed genome association analyses, using next-generation target resequencing, to evaluate the associations between the identified SNVs and PD. Methods: We obtained genomic DNA from 766 patients, who were clinically diagnosed with PD, and 336 healthy controls, all of Japanese origin. All data were analyzed using Ion AmpliSeq panel sequences, with 29 PD- or dementia-associated genes in a single panel. We excluded any variants that did not comply with the Hardy-Weinberg equilibrium in the control group. Variant frequencies in the PD and control groups were compared using PLINK. The identified variants were confirmed to a frequency difference of P < 0.05, after applying the Benjamini-Hochberg procedure using Fisher's exact test. The pathogenicity and prevalence of each variant were estimated based on a public gene database. Results: We identified three rare variants that were significantly associated with PD: rs201012663/rs150500694 in SYNJ1 and rs372754391 in DJ-1, which are intronic variants, and rs7412 in ApoE, which is an exonic variant. The variants in SYNJ1 and ApoE were frequently identified in the control group, and rs201012663/rs150500694 in SYNJ1 may play a protective role against PD. The DJ-1 variant was frequently identified in the PD group, with a high odds ratio of 2.2. Conclusion: The detected variants may represent genetic modifiers or disease-related variants in PD. Targeted-gene-panel resequencing may represent a useful method for detecting disease-causing variants and genetic association studies in PD.

Antidiabetic drugs for Alzheimer's and Parkinson's diseases: Repurposing insulin, metformin, and thiazolidinediones

Medical and scientific communities have been striving to disentangle the complexity of neurodegenerative diseases, particularly Alzheimer's disease (AD) and Parkinson's disease (PD), in order to develop a cure or effective treatment for these diseases. Along this journey, it has become important to identify the early events occurring in the prodromal phases of these diseases and the disorders that increase the risk of neurodegeneration highlighting common pathological features. This strategy has led to a wealth of evidence identifying diabetes, mainly type 2 diabetes mellitus (T2DM) as a main risk factor for the onset and progression of AD and PD. Impaired glucose metabolism, insulin resistance, and mitochondrial dysfunction are features common to both type 2 diabetes mellitus (T2DM), and AD and PD, and they appear before clinical diagnosis of the two neurodegenerative diseases. These could represent the strategic nodes of therapeutic intervention. Following this line of thought, a conceivable approach is to repurpose antidiabetic drugs as valuable agents that may prevent or reduce the risk of cognitive decline and neurodegeneration. This review summarizes the past and current findings that link AD and PD with T2DM, emphasizing the common pathological mechanisms. The efficacy of antidiabetic drugs, namely intranasal insulin, metformin, and thiazolidinediones, in the prevention and/or treatment of AD and PD is also discussed.

Role of DJ-1 in Immune and Inflammatory Diseases

The DJ-1 protein, known as an oxidative stress sensor, participates in the onset of oxidative stress-related diseases such as cancer, neurodegenerative disorders, type 2 diabetes, and male infertility. Although DJ-1 has been extensively studied for more than two decades, evidence has only recently emerged that it plays a key role in immune and inflammatory disorders. The immune regulatory function of DJ-1 is achieved by modulating the activation of several immune cells including macrophages, mast cells, and T cells via reactive oxygen species (ROS)-dependent and/or ROS-independent mechanisms. This review describes the current knowledge on DJ-1, focusing on its immune and inflammatory regulatory roles, and highlights the significance of DJ-1 as a novel therapeutic target for immune and inflammatory diseases.

Metformin as a Potential Neuroprotective Agent in Prodromal Parkinson's Disease-Viewpoint

To date, there are no clinically effective neuroprotective or disease-modifying treatments that can halt Parkinson's disease (PD) progression. The current clinical approach focuses on symptomatic management. This failure may relate to the complex neurobiology underpinning the development of PD and the absence of true translational animal models. In addition, clinical diagnosis of PD relies on presentation of motor symptoms which occur when the neuropathology is already established. These multiple factors could contribute to the unsuccessful development of neuroprotective treatments for PD. Prodromal symptoms develop years prior to formal diagnosis and may provide an excellent tool for early diagnosis and better trial design. Patients with idiopathic rapid eye movement behavior disorder (iRBD) have the highest risk of developing PD and could represent an excellent group to include in neuroprotective trials for PD. In addition, repurposing drugs with excellent safety profiles is an appealing strategy to accelerate drug discovery. The anti-diabetic drug metformin has been shown to target diverse cellular pathways implicated in PD progression. Multiple studies have, additionally, observed the benefits of metformin to counteract other age-related diseases. The purpose of this viewpoint is to discuss metformin's neuroprotective potential by outlining relevant mechanisms of action and the selection of iRBD patients for future clinical trials in PD.

Analysis of the Relationship between Type II Diabetes Mellitus and Parkinson's Disease: A Systematic Review

In the early sixties, a discussion started regarding the association between Parkinson's disease (PD) and type II diabetes mellitus (T2DM). Today, this potential relationship is still a matter of debate. This review aims to analyze both diseases concerning causal relationships and treatments. A total of 104 articles were found, and studies on animal and “in vitro” models showed that T2DM causes neurological alterations that may be associated with PD, such as deregulation of the dopaminergic system, a decrease in the expression of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), an increase in the expression of phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes 15 (PED/PEA-15), and neuroinflammation, as well as acceleration of the formation of alpha-synuclein amyloid fibrils. In addition, clinical studies described that Parkinson's symptoms were notably worse after the onset of T2DM, and seven deregulated genes were identified in the DNA of T2DM and PD patients. Regarding treatment, the action of antidiabetic drugs, especially incretin mimetic agents, seems to confer certain degree of neuroprotection to PD patients. In conclusion, the available evidence on the interaction between T2DM and PD justifies more robust clinical trials exploring this interaction especially the clinical management of patients with both conditions.

DJ-1 can form β-sheet structured aggregates that co-localize with pathological amyloid deposits

The loss of native function of the DJ-1 protein has been linked to the development of Parkinson's (PD) and other neurodegenerative diseases. Here we show that DJ-1 aggregates into β-sheet structured soluble and fibrillar aggregates in vitro under physiological conditions and that this process is promoted by the oxidation of its catalytic Cys106 residue. This aggregation resulted in the loss of its native biochemical glyoxalase function and in addition oxidized DJ-1 aggregates were observed to localize within Lewy bodies, neurofibrillary tangles and amyloid plaques in human PD and Alzheimer's (AD) patients' post-mortem brain tissue. These findings suggest that the aggregation of DJ-1 may be a critical player in the development of the pathology of PD and AD and demonstrate that loss of DJ-1 function can happen through DJ-1 aggregation. This could then contribute to AD and PD disease onset and progression.

DJ-1 in Parkinson's Disease: Clinical Insights and Therapeutic Perspectives

Mutations in the protein DJ-1 cause autosomal recessive forms of Parkinson’s disease (PD) and oxidized DJ-1 is found in the brains of idiopathic PD individuals. While several functions have been ascribed to DJ-1 (most notably protection from oxidative stress), its contribution to PD pathogenesis is not yet clear. Here we provide an overview of the clinical research to date on DJ-1 and the current state of knowledge regarding DJ-1 characterization in the human brain. The relevance of DJ-1 as a PD biomarker is also discussed, as are studies exploring DJ-1 as a possible therapeutic target for PD and neurodegeneration.

Role of DJ-1 in the mechanism of pathogenesis of Parkinson's disease

DJ-1 protein has multiple specific mechanisms to protect dopaminergic neurons against neurodegeneration in Parkinson's disease. Wild type DJ-1 can acts as oxidative stress sensor and as an antioxidant. DJ-1 exhibits the properties of molecular chaperone, protease, glyoxalase, transcriptional regulator that protects mitochondria from oxidative stress. DJ-1 increases the expression of two mitochondrial uncoupling proteins (UCP 4 and UCP5), that decrease mitochondrial membrane potential and leads to the suppression of ROS production, optimizes of a number of mitochondrial functions, and is regarded as protection for the neuronal cell survival. We discuss also the stabilizing interaction of DJ-1 with the mitochondrial Bcl-xL protein, which regulates the activity of (Inositol trisphosphate receptor) IP₃R, prevents the cytochrome c release from mitochondria and inhibits the apoptosis activation. Upon oxidative stress DJ-1 is able to regulate various transcription factors including nuclear factor Nrf2, PI3K/PKB, and p53 signal pathways. Stress-activated transcription factor Nrf2 regulates the pathways to protect cells against oxidative stress and metabolic pathways initiating the NADPH and ATP production. DJ-1 induces the Nrf2 dissociation from its inhibitor Keap1 (Kelch-like ECH-associated protein 1), promoting Nrf2 nuclear translocation and binding to antioxidant response elements. DJ-1 is shown to be a co-activator of the transcription factor NF-kB. Under nitrosative stress, DJ-1 may regulate PI3K/PKB signaling through PTEN transnitrosylation, which leads to inhibition of phosphatase activity. DJ-1 has a complex modulating effect on the p53 pathway: one side DJ-1 directly binds to p53 to restore its transcriptional activity and on the other hand DJ-1 can stimulate deacylation and suppress p53 transcriptional activity. The ability of the DJ-1 to induce activation of different transcriptional factors and change redox balance protect neurons against aggregation of α-synuclein and oligomer-induced neurodegeneration.

Critical Roles of Glutaredoxin in Brain Cells-Implications for Parkinson's Disease

SIGNIFICANCE

Glutaredoxin (Grx)1, an evolutionarily conserved and ubiquitous enzyme, regulates redox signal transduction and protein redox homeostasis by catalyzing reversible S-glutathionylation. Grx1 plays different roles in different cell types. In Parkinson's disease (PD), Grx1 regulates apoptosis signaling in dopaminergic neurons, so that loss of Grx1 leads to increased cell death; in microglial cells, Grx1 regulates proinflammatory signaling, so that upregulation of Grx1 promotes cytokine production. Here we examine the regulatory roles of Grx1 in PD with a view toward therapeutic innovation. Recent Advances: In postmortem midbrain PD samples, Grx1 was decreased relative to controls, specifically within dopaminergic neurons. In Caenorhabditis elegans models of PD, loss of the Grx1 homologue led to exacerbation of the neurodegenerative phenotype. This effect was partially relieved by overexpression of neuroprotective DJ-1, consistent with regulation of DJ-1 content by Grx1. Increased GLRX copy number in PD patients was associated with earlier PD onset; and Grx1 levels correlated with levels of proinflammatory tumor necrosis factor-α in mouse and human brain samples. In vitro studies showed Grx1 to be upregulated on proinflammatory activation of microglia. Direct overexpression of Grx1 increased microglial activation; silencing Grx1 diminished activation. Grx1 upregulation in microglia corresponded to increased neuronal cell death in coculture. Overall, these studies identify competing roles of Grx1 in PD etiology.

CRITICAL ISSUES

The dilemma regarding Grx1 as a PD therapeutic target is whether to stimulate its upregulation for neuroprotection or inhibit its proinflammatory activity.

FUTURE DIRECTIONS

Further investigation is needed to understand the preponderant role of Grx1 regarding dopaminergic neuronal survival.

Dysregulation of Glucagon Secretion by Hyperglycemia-Induced Sodium-Dependent Reduction of ATP Production

Diabetes is a bihormonal disorder resulting from combined insulin and glucagon secretion defects. Mice lacking fumarase (Fh1) in their β cells (Fh1βKO mice) develop progressive hyperglycemia and dysregulated glucagon secretion similar to that seen in diabetic patients (too much at high glucose and too little at low glucose). The glucagon secretion defects are corrected by low concentrations of tolbutamide and prevented by the sodium-glucose transport (SGLT) inhibitor phlorizin. These data link hyperglycemia, intracellular Na+ accumulation, and acidification to impaired mitochondrial metabolism, reduced ATP production, and dysregulated glucagon secretion. Protein succination, reflecting reduced activity of fumarase, is observed in α cells from hyperglycemic Fh1βKO and β-V59M gain-of-function KATP channel mice, diabetic Goto-Kakizaki rats, and patients with type 2 diabetes. Succination is also observed in renal tubular cells and cardiomyocytes from hyperglycemic Fh1βKO mice, suggesting that the model can be extended to other SGLT-expressing cells and may explain part of the spectrum of diabetic complications.

Effects of endurance training on hippocampus DJ-1, cannabinoid receptor type 2 and blood glucose concentration in diabetic rats

AIMS/INTRODUCTION

To investigate the effect of endurance training on hippocampus DJ-1 and cannabinoid receptor type 2 (CB2 ) protein and blood glucose concentration in diabetic rats.

MATERIALS AND METHODS

A total of 32 rats were randomly divided into diabetic (D), diabetic and exercise (DE), exercise (E) and control (C) groups. The endurance training was carried out five times per week for 6 weeks. The hippocampus DJ-1 and CB2 were measured using an enzyme-linked immunosorbent assay method.

RESULTS

The level of DJ-1 in the D group was significantly higher than the other groups (P ≤ 0.01). However, the level of DJ-1 was not significantly different between the C, E and DE groups. In addition, the level of CB2 was significantly lower in the D group compared with the other groups (P ≤ 0.01). Blood glucose was significantly higher in the D group compared with the DE group (P ≤ 0.05). Furthermore, a significant positive correlation between the level of DJ-1 and blood glucose was observed (r = 0.67, P ≤ 0.001). There was also a significant inverse correlation between the level of CB2 and blood glucose (r = -0.77, P ≤ 0.001).

CONCLUSIONS

The results of this study suggest that the level of DJ-1 and CB2 might change in response to diabetes, and regular aerobic exercise could mediate the effect of DJ-1 and CB2 on diabetes-induced neurodegenerative diseases.

PARK7 regulates inflammation-induced pro-labour mediators in myometrial and amnion cells

Preterm birth is a prevalent cause of neonatal deaths worldwide. Inflammation has been implicated in spontaneous preterm birth involved in the processes of uterine contractility and membrane rupture. Parkinson protein 7 (PARK7) has been found to play an inflammatory role in non-gestational tissues. The aims of this study were to determine the expression of PARK7 in myometrium and fetal membranes with respect to term labour onset and to elucidate the effect of PARK7 silencing in primary myometrium and amnion cells on pro-inflammatory and pro-labour mediators. PARK7 mRNA expression was higher in term myometrium and fetal membranes from women in labour compared to non-labouring samples and in amnion from preterm deliveries with chorioamnionitis. In human primary myometrial cells transfected with PARK7 siRNA (siPARK7), there was a significant decrease in IL1B, TNF, fsl-1 and poly(I:C)-induced expression of pro-inflammatory cytokine IL6, chemokines (CXCL8, CCL2), adhesion molecule ICAM1, prostaglandin PGF_2α and its receptor PTGFR. Similarly, amnion cells transfected with siPARK7 displayed a decrease in IL1B-induced expression of IL6, CXCL8 and ICAM1. In myometrial cells transfected with siPARK7, there was a significant reduction of NF-κB RELA transcriptional activity when stimulated with fsl-1, flagellin and poly(I:C), but not with IL1B or TNF. Collectively, our novel data describe a role for PARK7 in regulating inflammation-induced pro-inflammatory and pro-labour mediators in human myometrial and amnion cells.

Protective effects of Tat-DJ-1 protein against streptozotocin-induced diabetes in a mice model

A major feature of type 1 diabetes mellitus (T1DM) is hyperglycemia and dysfunction of pancreatic β-cells. In a previous study, we have shown that Tat-DJ-1 protein inhibits pancreatic RINm5F β-cell death caused by oxidative stress. In this study, we examined effects of Tat-DJ-1 protein on streptozotocin (STZ)-induced diabetic mice. Wild type (WT) Tat-DJ-1 protein transduced into pancreas where it markedly inhibited pancreatic β-cell destruction and regulated levels of serum parameters including insulin, alkaline phosphatase (ALP), and free fatty acid (FFA) secretion. In addition, transduced WT Tat-DJ-1 protein significantly inhibited the activation of NF-κB and MAPK (ERK and p38) expression as well as expression of COX-2 and iNOS in STZ exposed pancreas. In contrast, treatment with C106A mutant Tat-DJ-1 protein showed no protective effects. Collectively, our results indicate that WT Tat-DJ-1 protein can significantly ameliorate pancreatic tissues in STZ-induced diabetes in mice. [BMB Reports 2018; 51(7): 362-367].

DJ-1 Deficiency Protects Hepatic Steatosis by Enhancing Fatty Acid Oxidation in Mice

Our previous studies have shown that DJ-1 play important roles in progression of liver diseases through modulating hepatic ROS production and immune response, but its role in hepatic steatosis remains obscure. In the present study, by adopting a high-fat-diet (HFD) induced mice model, we found that DJ-1 knockout (DJ-1^-/-) mice showing decreased HFD-induced obesity and visceral adipose accumulation. In line with these changes, there were also reduced liver weight and ameliorated hepatic triglyceride (TG) accumulation in DJ-1^-/- mice compared to wild-type (WT) mice. And there were also decreased blood glucose levels and insulin resistance and reduced glucose metabolic disorder in DJ-1^-/- mice, whereas there were no significant differences in total cholesterol (TC) and serum lipid in two groups of mice. Mechanistically, we found that there were no differences in food intake in these two genotypes of mice. Furthermore, there were no significant differences in fatty acid synthesis and glycolysis, but the expression of key enzymes in fatty acid oxidation and the tricarboxylic acid (TCA) cycle, such as Cpt1α, Pparα, Acox1, Cs, Idh1 and Idh2, was increased in DJ-1^-/- mice liver, suggesting that there was enhanced fatty acids oxidation and TCA cycle in DJ-1^-/- mice. Our data indicate that deletion of DJ-1 enhancing fatty acids oxidation resulting in lower hepatic TG accumulation in mice, which protecting mice hepatic steatosis.

Ablation of DJ-1 impairs brown fat function in diet-induced obese mice

This study was conducted to investigate the effects of DJ-1 deficiency on brown adipose tissue (BAT) function in mice. DJ-1 knockout (KO) mouse models and wild-type littermates placed on a normal diet or high-fat diet were utilized to demonstrate the direct consequences of DJ-1 deletion on BAT characteristics, thermogenic ability, lipid metabolism, and microenvironment regulation. Global DJ-1 KO mice had defective brown adipose tissue activity culminating in a profound whitening of BAT. Despite aberrations in inactive BAT associated with greater lipid accretion, decreased sympathetic activity, mitochondrial dysfunction, reduced vascularity, and autophagy activation, we found that the body weight and energy balance were unaffected in male mice depleted of DJ-1. Taken together, the results of this study suggest that male DJ-1 KO mice exhibit defects in BAT activity but do not gain more weight, revealing that BAT activity is not necessarily required for predisposing DJ-1 KO mice to obesity. Therefore, therapeutic targeting of DJ-1 in BAT could provide novel insights into the treatment of obesity.

Fumarate Hydratase Deletion in Pancreatic β Cells Leads to Progressive Diabetes

We explored the role of the Krebs cycle enzyme fumarate hydratase (FH) in glucose-stimulated insulin secretion (GSIS). Mice lacking Fh1 in pancreatic β cells (Fh1βKO mice) appear normal for 6–8 weeks but then develop progressive glucose intolerance and diabetes. Glucose tolerance is rescued by expression of mitochondrial or cytosolic FH but not by deletion of Hif1α or Nrf2. Progressive hyperglycemia in Fh1βKO mice led to dysregulated metabolism in β cells, a decrease in glucose-induced ATP production, electrical activity, cytoplasmic [Ca²⁺]_i elevation, and GSIS. Fh1 loss resulted in elevated intracellular fumarate, promoting succination of critical cysteines in GAPDH, GMPR, and PARK 7/DJ-1 and cytoplasmic acidification. Intracellular fumarate levels were increased in islets exposed to high glucose and in islets from human donors with type 2 diabetes (T2D). The impaired GSIS in islets from diabetic Fh1βKO mice was ameliorated after culture under normoglycemic conditions. These studies highlight the role of FH and dysregulated mitochondrial metabolism in T2D.

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Fh1 loss in β cells causes progressive Hif1α-independent diabetes

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Fh1 loss in β cells impairs ATP generation, electrical activity, and GSIS

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Elevated fumarate is a feature of diabetic murine and human islets

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“Normoglycemia” restores GSIS in Fh1βKO islets

Insulin signaling pathway protects neuronal cell lines by Sirt3 mediated IRS2 activation

Cellular stress like ER and oxidative stress are the principle causative agents of various proteinopathies. Multifunctional protein PARK7/DJ-1 provides protection against cellular stress. Recently, insulin/IGF also has emerged as a neuro-protective molecule. However, it is not known whether DJ-1 and insulin/IGF complement each other for cellular protection in response to stress. In this study, we show for the first time, that in human and mouse neuronal cell lines, down regulation of DJ-1 for 48 h leads to compensatory upregulation of insulin/IGF signaling (IIS) pathway genes, namely, insulin receptor, insulin receptor substrate, and Akt under normal physiological conditions as well as in cellular stress conditions. Moreover, upon exogenous supply of insulin there is a marked increase in the IIS components both at gene and protein levels leading to down regulation and inactivation of GSK3β. By immunoprecipitation, it was observed that Sirt3 mediated deacetylation and activation of FoxO3a could not occur under DJ-1 downregulation. Transient DJ-1 downregulation also led to Akt mediated increased phosphorylation and nuclear exclusion of FoxO3a. When DJ-1 was downregulated increased interaction of Sirt3 with IRS2 was observed leading to its activation resulting in IIS upregulation. Thus, transient downregulation of DJ-1 leads to stimulation of IIS pathway by Sirt3 mediated IRS2 activation. Consequently, antiapoptotic program is triggered in neuronal cells via Akt-GSK3β-FoxO3a axis. © 2018 BioFactors, 44(3):224-236, 2018.

Introduction/Overview

The DJ-1 gene is an oncogene and also causative gene for a familial form of Parkinson disease. Although exits of cancer and neurodegenerative diseases, including Parkinson disease, are completely opposite, there are some common points of view between both diseases, including growth and death signaling pathways, and oxidative stresses affect the onset and pathogenesis of both cancer and neurodegenerative diseases. DJ-1 has versatile functions and plays a role in protection against oxidative stress. Inactivation and/or excess activation of DJ-1 functions, therefore, leads to onsets of oxidative stress-related diseases such as type 2 diabetes and male infertility in addition to cancer and neurodegenerative diseases, and studies about DJ-1 will give rise to the common mechanism among these diseases. Furthermore, secreted DJ-1 levels in serum and DJ-1-binding compounds will be a diagnostic biomarker and therapeutic drug for neurodegenerative diseases, respectively.

DJ‑1 alleviates high glucose‑induced endothelial cells injury via PI3K/Akt‑eNOS signaling pathway

Hyperglycemia mediated endothelial cells (ECs) injury is closely associated with diabetic vascular complications. It was revealed that DJ‑1 possesses cellular protective effects by suppressing oxidative stress. The present study aimed to investigate the beneficial effects of DJ‑1 on high glucose (HG)‑induced human umbilical vein endothelial cell (HUVEC) injury and to elucidate its underlying mechanisms. HUVECs were incubated under 5.5 mM (control group) or 25 mM D‑glucose (HG group) and then transfected with recombinant adenoviral vectors to overexpression of DJ‑1. Cell proliferation and apoptosis were measured using the EdU incorporation assay and flow cytometry with Annexin V-FITC/propidium iodide double staining, respectively. Apoptotic‑related proteins were determined using western blot analysis. Reactive oxygen species (ROS) production, lactate dehydrogenase (LDH) and nitric oxide (NO) levels, the content of malondialdehyde (MDA), and the activities of superoxide dismutase (SOD) were measured. Results demonstrated that overexpression of DJ‑1 promoted cell proliferation and inhibited HUVECs apoptosis stimulated by HG. DJ‑1 also suppressed the HG‑induced reduction in the Bcl‑2/Bax ratio and HG activated ROS generation in HUVECs. Furthermore, HG significantly increased the levels of LDH and MDA, and reduced the level of SOD; however, these effects were reversed by Ad‑DJ‑1 transfection. Furthermore, the cellular protective effect of overexpression of DJ‑1 enhanced p‑Akt/Akt ratio, eNOS activation and NO production, and these trends were partially reversed by a phosphatidylinositol‑4,5‑bisphosphate 3‑kinase (PI3K) inhibitor (LY294002). Taken together, the present study highlighted the involvement of DJ‑1 in HG‑related EC injury and identified that DJ‑1 exerts a cellular protective effect in HUVECs exposed to HG induced oxidative stress via activation of the PI3K/Akt‑eNOS signaling pathway.

Structural features of human DJ-1 in distinct Cys106 oxidative states and their relevance to its loss of function in disease

DJ-1 (PARK7) is a multifunctional protein linked to the onset and progression of a number of diseases, most of which are associated with high oxidative stress. The Cys106 of DJ-1 is unusually reactive and thus sensitive to oxidation, and due to high oxidative stress it was observed to be in various oxidized states in disease condition. The oxidation state of Cys106 of DJ-1 is believed to determine the specific functions of the protein in normal and disease conditions. Here we report molecular dynamics simulation and biophysical experimental studies on DJ-1 in reduced (Cys106, S^-), oxidized (Cys106, SO₂^-), and over-oxidized (Cys106, SO₃^-) states. To simulate the different oxidation states of Cys106 in DJ-1, AMBER related force field parameters were developed and reported for 3-sulfinoalanine and cysteine sulfonic acid. Our studies found that the overall structure of DJ-1 in different oxidation states was similar globally, while it differed locally significantly, which have implications on its stability, function and its link to disease on-set. Importantly, the results suggest that over-oxidation may trigger loss of functions due to local structural modification in the Cys106 containing pocket of DJ-1 and structurally destabilize the dimeric state of DJ-1, which is believed to be its bioactive conformation. Such loss of functions would result in reduced ability of DJ-1 to protect from oxidative stress insults and may lead to increased progression of disease.

The Role of Interleukin-18, Oxidative Stress and Metabolic Syndrome in Alzheimer's Disease

The role of interleukins (ILs) and oxidative stress (OS) in precipitating neurodegenerative diseases including sporadic Alzheimer's disease (AD), requires further clarification. In addition to neuropathological hallmarks-extracellular neuritic amyloid-β (Aβ) plaques, neurofibrillary tangles (NFT) containing hyperphosphorylated tau and neuronal loss-chronic inflammation, as well as oxidative and excitotoxic damage, are present in the AD brain. The pathological sequelae and the interaction of these events during the course of AD need further investigation. The brain is particularly sensitive to OS, due to the richness of its peroxidation-sensitive fatty acids, coupled with its high oxygen demand. At the same time, the brain lack robust antioxidant systems. Among the multiple mechanisms and triggers by which OS can accumulate, inflammatory cytokines can sustain oxidative and nitrosative stress, leading eventually to cellular damage. Understanding the consequences of inflammation and OS may clarify the initial events underlying AD, including in interaction with genetic factors. Inflammatory cytokines are potential inducers of aberrant gene expression through transcription factors. Susceptibility disorders for AD, including obesity, type-2 diabetes, cardiovascular diseases and metabolic syndrome have been linked to increases in the proinflammatory cytokine, IL-18, which also regulates multiple AD related proteins. The association of IL-18 with AD and AD-linked medical conditions are reviewed in the article. Such data indicates that an active lifestyle, coupled to a healthy diet can ameliorate inflammation and reduce the risk of sporadic AD.

DJ-1 maintains energy and glucose homeostasis by regulating the function of brown adipose tissue

DJ-1 protein is involved in multiple physiological processes, including Parkinson’s disease. However, the role of DJ-1 in the metabolism is largely unknown. Here we found that DJ-1 maintained energy balance and glucose homeostasisvia regulating brown adipose tissue (BAT) activity. DJ-1-deficient mice reduced body mass, increased energy expenditure and improved insulin sensitivity. DJ-1 deletion also resisted high-fat-diet (HFD) induced obesity and insulin resistance. Accordingly, DJ-1 transgene triggered autonomous obesity and glucose intolerance. Further BAT transplantation experiments clarified DJ-1 regulates energy and glucose homeostasis by modulating BAT function. Mechanistically, we found that DJ-1 promoted PTEN proteasomal degradation via an E3 ligase, mind bomb-2 (Mib2), which led to Akt activation and inhibited FoxO1-dependent Ucp1 (Uncoupling protein-1) expression in BAT. Consistently, ablation of Akt1 mitigated the obesity and BAT dysfunction induced by DJ-1 transgene. These findings define a new biological role of DJ-1 protein in regulating BAT function, with an implication of the therapeutic target in the treatment of metabolic disorders.

The Role of the Antioxidant Protein DJ-1 in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a worldwide escalating health disorder resulting from insulin resistance and functional loss of insulin-producing beta cells that finally cause chronically elevated blood glucose concentrations. Here we review the role of ubiquitously expressed antioxidant protein DJ-1 in the pathogenesis of T2DM. In beta cells, DJ-1 protects against oxidative stress, endoplasmic reticulum stress, and streptozotocin- and cytokine-induced stress and preserves beta cell viability and insulin secretion. In skeletal muscle, DJ-1 controls energy metabolism and efficient fuel utilization, whereas in adipose tissue a role in adipogenesis and obesity-induced inflammation has been reported. This suggests that DJ-1 plays multiple roles in many cell types under metabolically challenging conditions as seen in obesity, insulin resistance, and T2DM.

Mitochondrial control of cell bioenergetics in Parkinson's disease

Parkinson disease (PD) is a neurodegenerative disorder characterized by a selective loss of dopaminergic neurons in the substantia nigra. The earliest biochemical signs of the disease involve failure in mitochondrial-endoplasmic reticulum cross talk and lysosomal function, mitochondrial electron chain impairment, mitochondrial dynamics alterations, and calcium and iron homeostasis abnormalities. These changes are associated with increased mitochondrial reactive oxygen species (mROS) and energy deficiency. Recently, it has been reported that, as an attempt to compensate for the mitochondrial dysfunction, neurons invoke glycolysis as a low-efficient mode of energy production in models of PD. Here, we review how mitochondria orchestrate the maintenance of cellular energetic status in PD, with special focus on the switch from oxidative phosphorylation to glycolysis, as well as the implication of endoplasmic reticulum and lysosomes in the control of bioenergetics.

Sex effect on insulin secretion and mitochondrial function in pancreatic beta cells of elderly Wistar rats

AIMS/HYPOTHESIS

Glucose tolerance progressively declines with age, and there is a high prevalence of type 2 diabetes in the elderly people. Previous studies have reported the sex differences in risk for type 2 diabetes, especially in the elderly people, whereas reasons for these sex differences remain poorly understood. This study aims to evaluate the effect of sex on glucose-stimulated insulin secretion and mitochondrial function in pancreatic beta cells of Wistar rats.

METHODS

3-month-old and 18-month-old Wistar rats of both sexes were used. Insulin secretion of islets was analyzed by glucose-stimulated insulin secretion and islet perifusion assays; ATP content and oxygen consumption rate of islets were determined to evaluate the mitochondrial function.

RESULTS

Insulin secretion of islets under high glucose conditions declined significantly with age in both sexes. Glucose-stimulated insulin secretion of elderly female groups was markedly higher than that of male groups under high glucose conditions. Importantly, islets from elderly female groups showed higher mitochondrial function compared with male counterparts, evidenced by higher ATP content and oxygen consumption rate under high glucose conditions. It was also noted that mitochondrial biogenesis of islets from elderly female rats was significant higher compared with male rats. There were notable increases in expression of genes involved in mitochondrial biogenesis in islets from elderly female rats compared with male rats.

CONCLUSION

This study demonstrates a sex dimorphism in the age-associated impairment of pancreatic beta cell function in elderly rats, while the potential mechanism may be related to the sexual differences in mitochondrial biogenesis and function.

Overexpression of DJ-1 reduces oxidative stress and attenuates hypoxia/reoxygenation injury in NRK-52E cells exposed to high glucose

Patients with diabetes are more vulnerable to renal ischemia/reperfusion (I/R) injury, which is implicated in hyperglycemia-induced oxidative stress. We previously reported that the hyperglycemia-induced inhibition of DJ-1, a novel oncogene that exhibits potent antioxidant activity, is implicated in the severity of myocardial I/R injury. In the present study, we aimed to explore the role of DJ-1 in hypoxia/reoxygenation (H/R) injury in renal cells exposed to high glucose (HG). For this purpose, NRK-52E cells were exposed to HG (30 mM) for 48 h and then exposed to hypoxia for 4 h and reoxygenation for 2 h, which significantly decreased cell viability and superoxide dismutase (SOD) activity, and increased the malondialdehyde (MDA) content, accompanied by a decrease in DJ-1 protein expression. The overexpression of DJ-1 by transfection with a DJ-1 overexpression plasmid exerted protective effects against HG-induced H/R injury, as evidenced by increased CCK-8 levels and SOD activity, the decreased release of lactate dehydrogenase (LDH) and the decreased MDA content, and increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1) expression. Similar effects were observed following treatment with the antioxidant, N-acetylcysteine. These results suggest that the overexpression of DJ-1 reduces oxidative stress and attenuates H/R injury in NRK-52E cells exposed to HG.